6
What is your "Default Template Set" in "System" -> "Preferences" -> "General Settings"
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If it is set to anything other than "Default" go to "System" -> "Templates". Now go into the mydownloads templates for the default set. Now download "mydownloads_index.html"
Go back to "System" -> "Templates" and going into the mydownloads template for your custom set.
Upload the template saved before for "mydownloads_index.html"
Now try going to your page again.
If you still have problems, you could try deleting all the files in the /template_c/ directory. Maybe the template just needed to be recreated.